A cohort of patients manifesting early dyskinesia have been identified and followed with repeated ratings and videotaped recordings. Preliminary analyses of the first 53 patients completing a year or more of followup has been completed. Support is now requested to increase the early dyskinesia sample to over 200 patients and to follow them from two to six years. The change in early dyskinesia over time will be assessed and factors affecting the course of dyskinesia including antipsychotic drug therapy and other patient characteristics will be studied. A complimentary group of patients with late persistent dyskinesia will also be followed for two to four years. Their course will be compared with that of the early dyskinesia patients. Neuroleptic plasma levels will be added to the periodic ratings both to determine the relations between such levels and changes in dyskinesia and to determine whether such levels predict clinical relapse or other side effects. A double-blind study of patients on depot fluphenazine decanoate is also proposed involving sixty patients, twenty of whom will remain on their original dose while forty will have their dose decreased 40%. The relationships between neuroleptic plasma levels, psychiatric status, dyskinesia, and neurological side effects will be studied as will phenomena suggestive of supersensitivity psychosis.